Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C2300/00—Process aspects
  • C21C2300/02—Foam creation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the invention relates to a process for the formation of foam slag of a stainless melt in an AOD (argon oxygen decarburization) or MRP (metallurgical refining process) converter or CONARC SSt for stainless steel by adding a foaming material.
• AOD argon oxygen decarburization
• MRP metalurgical refining process
• CONARC SSt for stainless steel by adding a foaming material.
• a slag is formed which contains a high proportion of metal oxides, especially of chromium oxide.
• concentration of chromium oxide during the refining phase often reaches values higher than 20%, which greatly increases the viscosity of the slag.
• the slag is usually very hard shortly before the reduction.
• the reaction (3) is of fundamental importance for the production of stainless steel, since chromium oxide is the most important constituent in the formation of foam slag. However, this reaction takes place in the conventional process to a very small extent. The reason is the high viscosity of the Slag. All conventional converter processes reduce the slag only in the subsequent step, in the so-called reduction, whereby the process is usually carried out with silicon in the form of ferrosilicon. However, if the slag viscosity is suitable for foaming, the reduction process (equation 3) is made possible by the gaseous CO formed by the refining process itself as well as by the iron oxide reduction of the foam material. This is added to the melt in the form of pellet or briquette at a given time. The main components of the material are iron oxide carriers such as tinder, then carbon and a baiast material, which defines a targeted placement of the briquette in the melt.
• Critical to the formation of foam slag are thus the constituents of the foaming material added and the slag viscosity, which in turn depends on the composition and the temperature of the molten slag. Above all, the viscosity defines a state region of the molten slag in which foaming is possible. It is therefore important to control the slag basicity responsible for the viscosity, which forces the resulting gas bubbles to remain temporarily in the slag layer.
• the phenomenon of bubble formation is a process that utilizes the mechanical force of the reacting gas bubbles to create a new surface area in the slag.
• the buoyant forces on the gas bubbles temporarily split the slag surface and saturate the entire slag layer to make the foam.
• the number of accumulating bubbles increases with increasing foam.
• the height of the foam layer increases with increasing amount of gas, it is directly proportional to the amount of foaming material.
• DE 10 2007 006 529 A1 additionally reduces the metal oxides present in the slag, predominantly chromium oxide, by the briquettes and / or pellets floating close to the phase boundary melt / slag, the resulting reaction gases being the Support slag foaming.
• the briquettes or pellets charged into the electric arc furnace consist of a defined mixture of an iron carrier as ballast material, carbon or carbon as reducing agent and a binder.
• a slag is formed which contains a high proportion of chromium oxide.
• the chromium oxide concentration often reaches values as mentioned above above 20%, which is why such slags can not be liquefied and foamed to the desired extent due to their composition. It is an object of the invention to develop a method by which the known successful methods for slag foaming in an electric furnace can also be used in a converter.
• the object is achieved with the characterizing features of claim 1, characterized in that a previously defined mixture of a metal oxide, iron carrier, carbon and binder material in the form of pellets or briquettes is entered into the converter and chemically under the slag layer due to the high ambient temperature reacting reducing, in particular by the reduction process of the metal oxide with the carbon formed carbon monoxide gas causes the SchumaufWarumen with its gas bubbles and wherein the specific gravity of the material and the dissolution time of the reduction process are chosen so that an optimal blistering in terms of size and Duration is reached.
• the foamed slag develops quasi exponentially according to the structure of the defined mixture consisting of a metal oxide, iron carrier, carbon and binding material in the form of pellets or briquettes.
• the mixture undergoes a solution process with parallel reduction of the iron oxide due to the prevailing high ambient temperature.
• the pellet or briquette is immediately encased in a shell of solidified metal when entering this zone because of its colder temperature. Since the average melting temperature of the pellet or briquette is lower than that of the metal, a melting process of the mixture takes place within the shell. Depending on the temperature difference, the reduction process within the shell is terminated either earlier than the shell melting or later. In the first In the event, the process may result in bursting of the granules and explosive release of the CO gas bubble, causing greater metal / slag intermixing.
• the CO gas bubble will freely develop in the zone between the slag and the molten metal.
• the addition of the foaming material by a specific control with values between 2 - 30 kg pellets or briquettes / t liquid metal / min. performed so that a defined foam slag height is obtained and also remains over a previously defined time.
• the distribution of this addition of foaming material takes place layer by layer and nationwide with a defined areal density and is for an optimum foaming effect between 1 - 5 kg / m 2 / min.
• the slag fulfills its primary function by the capture of unwanted components from the melt. Due to the weak thermal conductivity of the foamed slag, the heat losses are greatly reduced, thus improving the energy input into the metallic melt.
• the foamed slag also means a strong soundproofing.
• the foam-coated top lance emits little noise into the environment, thereby improving the environmental conditions in the area of the converter.
• an inventive SchlackenaufCumen is shown below. Above a molten metal 1 present in a converter (the converter is not shown), a slag layer 2 with embedded pellets 4 is floating on the molten metal 1. These pellets 4 were previously filled into the converter, where they are set in advance Jardinten and because of their training with a shell 6 of solidified metal initially in the zone 3 between the slag layer 2 and the molten metal 1 order. After melting of this shell 6 and correspondingly lighter some pellets 4 have left the zone 3 and are within the slag layer 2. The resulting from the reduction of existing in the pellets 4 iron oxide carriers and existing limestone (CaCOs) CO / CO 2 gas bubbles. 7 have led to the formation of a foam slag layer 8, in which the CO / CO 2 gas bubbles 7 are shown enlarged.
• CaCOs existing limestone
• a pellet 4 made of a mixture 5 with exemplary ingredients (CO, CO 2 , Fe, Cr, CaO) and with a shell 6 of solidified metal formed in zone 3 is likewise shown enlarged.
• exemplary ingredients CO, CO 2 , Fe, Cr, CaO

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Carbon Steel Or Casting Steel Manufacturing (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

Priority Applications (9)

Applications Claiming Priority (2)

Publications (1)

Family

ID=43567490

Family Applications (1)

Country Status (11)

Families Citing this family (5)

Citations (4)

Family Cites Families (12)

• 2010
  • 2010-01-19 DE DE102010004983A patent/DE102010004983A1/de not_active Withdrawn
• 2011
  • 2011-01-05 EP EP11700327.7A patent/EP2526211B1/de not_active Not-in-force
  • 2011-01-05 CN CN201180014480.1A patent/CN102791888B/zh not_active Expired - Fee Related
  • 2011-01-05 KR KR1020127021352A patent/KR101507398B1/ko not_active Expired - Fee Related
  • 2011-01-05 MY MYPI2012700474A patent/MY184459A/en unknown
  • 2011-01-05 RU RU2012135467/02A patent/RU2518837C2/ru not_active IP Right Cessation
  • 2011-01-05 US US13/522,637 patent/US8747518B2/en active Active
  • 2011-01-05 WO PCT/EP2011/050079 patent/WO2011089027A1/de not_active Ceased
  • 2011-01-05 CA CA2787278A patent/CA2787278C/en not_active Expired - Fee Related
  • 2011-01-05 BR BR112012017822A patent/BR112012017822A8/pt active Search and Examination
• 2012
  • 2012-07-16 ZA ZA2012/05256A patent/ZA201205256B/en unknown

Patent Citations (4)

Also Published As

Similar Documents

Legal Events